NaCl: Update revision in DEPS, f418b37 -> cc78fa0

This pulls in the following Native Client changes:

4db937c: (jfb@chromium.org) Update revision for PNaCl
db53905: (jvoung@chromium.org) PNaCl: Update LLVM revision in pnacl/COMPONENT_REVISIONS
04b09f1: (jfb@chromium.org) PNaCl: Update LLVM revision in pnacl/COMPONENT_REVISIONS
924decd: (hidehiko@chromium.org) Non-SFI mode: Enable C++11 features on gyp build.
7fe2747: (jfb@chromium.org) Overflow test: improve testing of signed values around 0
d632af2: (jfb@chromium.org) Update revision for PNaCl
cc78fa0: (sbc@chromium.org) Update sysroot creator scripts toolchain.

Changes: https://chromium.googlesource.com/native_client/src/native_client/+log/f418b37b22393d82c08d28ce1c151bed933d2c9b..cc78fa093218f9a9a5e576002e197e17da379023

BUG=none
TEST=browser_tests and nacl_integration
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_chromium_dbg_32_ng,linux_arm_compile,linux_nacl_sdk_build

Review URL: https://codereview.chromium.org/1022923004

Cr-Commit-Position: refs/heads/master@{#321511}

DEPS

@@ -94,7 +94,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling NaCl
   # and whatever else without interference from each other.
-  'nacl_revision': 'f418b37b22393d82c08d28ce1c151bed933d2c9b',
+  'nacl_revision': 'cc78fa093218f9a9a5e576002e197e17da379023',
 }
 
 # Only these hosts are allowed for dependencies in this DEPS file.